Such smoke detectors can be used e.g. in the passenger or baggage compartments of an aircraft, in order to detect a fire promptly by the smoke that develops. After a fire has been detected, suitable fire extinguishing efforts can be introduced. With regard to a baggage compartment or cargo hold, for example, it is possible to first flood the entire compartment or hold with a high dose of a gaseous extinguishing medium, in order to extinguish the fire, and subsequently, until the end of the flight, to maintain a minimum concentration of extinguishing medium in the contained atmosphere.
In order to avoid damage of the smoke detectors, as well as to avoid hindrances by the detectors, they are preferably mounted in a recessed manner in a ceiling, as mentioned. Enclosure shells or mounting housings are used for this purpose and the smoke detectors are secured by screws in the housing or shell, to encapsulate the detectors in the ceiling structure, except for the smoke entrance that remains open so that developing smoke can stream into the enclosure shell to reach the detector. Due to the flow dynamic conditions to which the smoke stream is exposed as it travels through the smoke entrance and due to the volume of the enclosure shell a certain length of time passes, before the smoke concentration within the enclosure shell is sufficient to produce a signal by triggering the detector. Due to the resulting delay it is not always ensured under all circumstances, that the prescribed short response times are met.